The object of the present research is to study the role of prostaglandins in human and experimental hypertension and in the control of sodium balance. Preliminary experiments suggest that prostaglandin A is decreased by sodium loading and increased by sodium depletion and that prostaglandin A is elevated in rats with spontaneous hypertension. A continuation of these studies will include a study of the effect of changes in sodium intake on prostaglandin levels in normal humans and subjects with various forms of hypertension and in pregnant subjects. The role of the pregnant uterus in prostaglandin production will be evaluated. A study of the mechanism of prostaglandin A release from the kidney will be carried out in man and animals with particular emphasis on the relationship of renin secretion to PGA secretion.